Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

662
FXUS63 KLOT 191122
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
622 AM CDT Sun Apr 19 2026

.KEY MESSAGES...

- Gusty and seasonably cool today.

- Potential (20-40%) for some gusty showers late this morning
  and afternoon.

- Frost/freeze conditions are expected outside of Chicago and
  central Cook County late tonight into Monday morning.

&&

.DISCUSSION...
Issued at 232 AM CDT Sun Apr 19 2026

It`s a chilly start to our Sunday with temperatures sitting in
the middle and upper 30s early this morning. Mostly clear skies
currently will cloud up through the morning with the arrival of
a shortwave disturbance traversing the windward side of the
broader upper trough. This wave will work across northern IL and
drag a back door cold frontal feature southward across the CWA
this morning into afternoon. The wave is sharpening up over the
northern Plains this morning and is bringing pockets of light
precip to the eastern Dakotas and Minnesota. Steep lapse rates
between 8 and 9 K/km from the surface to 700-650 mb and low
level moisture advection ahead of the front will generate a
layer of surface-based instability with the frontal passage.
Some decent low level forcing also looks to accompany the front.
Put together, we have a good signal for at least some light
precip, but some not-so-light precip is on the table as well.

It`s unclear exactly how much we`ll destabilize with some camps
suggesting that dewpoints will mix down for the afternoon and
the dry near-surface air could help relegate precip to largely
sprinkles. Other camps, such as the more recent RAP runs, are
more optimistic with the thermodynamics such that a few embedded
lightning strikes may even be possible. Guidance resolves
largely trace amounts to a couple of hundredths of QPF with
this, but a number of high res camps depict streaks of higher
amounts closer to or in excess of a tenth, suggesting some
pockets of more moderate rainfall are certainly possible. Precip
will move into our north and northwest CWA during the mid-late
morning and across the I-55 corridor by early afternoon. The
primary target area for precip coverage will be near and north
of a roughly LaSalle-to-Rensselaer line along the track of the
wave while areas farther south should stay dry. Precip should
end in our CWA by early evening as the wave pulls away to the
east.

Another question to consider is will we see any snow or wintry
mix with precip today? While surface temps will be in the 40s to
near 50 during the event, wet bulb zero heights as low as 1,000
feet off the ground may allow some snow flakes to reach the
surface. Given the convective nature of the precip and
instability extending through the DGZ, a bonafide graupel shower
could even be in the cards. Better snow/mix chances may exist
across our north/northwest this morning given the earlier timing
before the BL can heat up. Additionally, while the stronger
signal for precip exists immediately ahead of the front, there
is a potential for some light post-frontal precip into early
evening which also has a seemingly better shot at featuring some
snow. However, the wintry precip potential appears to be a low
one and in the forecast, went with practically all liquid PoPs.

Deep mixing will into an elevated low level wind field will
also promote gusty winds today. Again, uncertainty exists in the
depth and efficiency of mixing, but the potential is there for
occasional gusts over 40 mph, especially closer to central IL.
More frequent wind gusts look to be in the 25 to 35 mph range
with the strongest winds generally expected south of I-80. Winds
will start out westerly today before veering to northwest for
the afternoon with the frontal passage. Afternoon temperatures
will range from the middle and upper 40s in our north to middle
50s in our south.

Surface high pressure will center over the area late tonight
into early Monday. There won`t be much noteworthy cold advection
behind the front, but the resultant clear skies and calm winds
will bring slightly cooler conditions to tonight/Monday
morning. With lows still looking like upper 20s and lower 30s,
decided to upgrade our Freeze Watch to a Freeze Warning for the
entire CWA outside of central Cook County where conditions will
likely stay a few degrees warmer.

Lower and middle 50s are forecast for Monday with mostly sunny
skies. Behind the departing trough, upper ridging scooting east
into the Plains will advect a much milder airmass and the
eastern edge of an EML into the region for Tuesday. Highs are
currently forecast to reach the 70s around the CWA. A shortwave
feature embedded in the upper flow may attempt to produce some
showers Tuesday evening and night, but lots of capping and
little forcing favor largely dry conditions. The upper ridge
will center over the area on Wednesday and middle to upper 70s
are forecast away from the lake. Winds turning onshore will keep
areas near the lake notably cooler on Wednesday; lakeside highs
are forecast in the 50s. Lower 80s are forecast on Thursday
ahead of a large synoptic system that will move across the area
and bring additional rain and storm chances to late Thursday and
Friday.

Doom

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 622 AM CDT Sun Apr 19 2026

- Scattered showers develop later this morning and afternoon.
  Chance for a little snow mixing in at RFD, but no
  accumulations would occur.

- Winds turn WNW/NW and will become gusty into the afternoon.
  Potential for a few 30+ kt gusts during a brief window towards
  midday.

- Wind shift to northeasterly this evening and overnight. Small
  chance for MVFR stratus near the lake overnight.

Light southwesterly winds will increase and become gusty WNW/NW
through the morning and afternoon. Deep mixing may support a
brief period of stronger wind gusts (30+ kts), but this
potential appears too brief and uncertainty too high to justify
adding to the TAFs.

A fast-moving disturbance currently racing across southeast
Minnesota will move into the region later this morning and
afternoon. Based on upstream radar returns and observations,
combined with the strong nature of forcing associated with this
feature, have converted the previous PROB30s to TEMPOs or
showers. At RFD: have included a mention of -SHRASN due to the
slightly earlier arrival (towards 15z) and cooler conditions.
At the Chicago-area terminals: can`t entirely rule out a
snowflake or some graupel if more robust convective showers
develop, but these chances appear too low to include in the
TEMPO groups. Air temperatures at all sites will be above
freezing during any precipitation. There is a chance some spotty
shower activity lingers near ORD, MDW, and GYY beyond the
current TEMPO groups, but this signal has diminished some from
previous guidance.

A northeast wind shift will occur at ORD, MDW, and GYY this
evening, although some uncertainty regarding the precise timing
remains. There is a small potential (30 percent or less) of some
MVFR cigs developing off the lake this evening. Eventually,
winds will trend light/variable overnight into Monday morning
before gradually becoming very light southwesterly towards
midday Monday. A lake breeze will push inland through Monday
afternoon.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Frost Advisory until 9 AM CDT this morning for ILZ003-ILZ004-
     ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
     ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ106-ILZ107-
     ILZ108.

     Freeze Warning from midnight tonight to 9 AM CDT Monday for
     ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
     ILZ103-ILZ105-ILZ106-ILZ107-ILZ108.

IN...Frost Advisory until 9 AM CDT /10 AM EDT/ this morning for
     INZ001-INZ002-INZ010-INZ011-INZ019.

     Freeze Warning from midnight CDT /1 AM EDT/ tonight to 9 AM
     CDT /10 AM EDT/ Monday for INZ001-INZ002-INZ010-INZ011-
     INZ019.

LM...Small Craft Advisory from 11 AM this morning to 7 PM CDT this
     evening for the IL and IN nearshore waters.

&&

$$

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